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Haemotology > Week 1 (part 2) > Flashcards

Week 1 (part 2) Flashcards

1
Q

Haematicinic deficiency

A

Deficiency in the nutrients, including iron, folic acid

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2
Q

Why is unnecessary transfusion carried out sometimes?

A

Failure to identify anaemia and its haematinic deficiency (usually iron) in advance 13%

Failure to treat a known haematinic deficiency (usually iron) in advance – ie one already diagnosed 5%

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3
Q

Why do blood donor samples have to undergo microbiological testing?

A

HIV, Hep B, Hep C, Hep E, HTLV, Syphilis

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4
Q

Blood components

A

Red cells, FFP, platelets, cryoprecipitate

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5
Q

Blood products

A

Anti-D immunoglobulin, prothrombin complex concentrate

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6
Q

ABO blood system

A

Encoded by the ABO gene on chromosome 9.

We each inherit two ABo genes (one from each parent). If we have an A gene, then we have the A antigen expressed on our red cells. If we express the B gene, the B antigen will be expressed on our red cells.

A’ and ‘B’ genes code for transferases which modify precursor called ‘H substance’ on red cell membrane.

• A and B are dominant over O
• A and B are co-dominant
• O is silent

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7
Q

ABO group A

A

Antigens present on red cells is A

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8
Q

ABO group B

A

Antigens present on red cells is B

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9
Q

ABO group AB

A

Antigen present on red cells is A & B

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10
Q

ABO group 0

A

Antigen present on red cells is neither A or B

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11
Q

Genotype and phenotype

A
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12
Q

Inheritance of ABO system

A
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13
Q

Landsteiner’s Law

A

Individuals produce antibodies to the antigen that they lack on their red cells. Landsteiner’s law states that, for whichever ABO antigen is not present on the red cells, the corresponding antibody is found in the plasma

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14
Q

Landsteiner’s law table

A
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15
Q

Blood compatibility table

A
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16
Q

RhD antigens

A
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17
Q

Why is RhD important to know about?

A

• Very immunogenic
• Anti-D antibody can cause transfusion reactions and haemolytic disease of the fetus and newborn

• Avoid exposing RhD negative people to D antigen through transfusion
– RhD negative blood to RhD negative people

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18
Q

Aims of pre-transfusion testing

A

Identify ABO and RhD group of patient

Identify presence of clinically significant red cell antibodies

allow selection of appropriate blood for transfusions

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19
Q

Antisera

A

Reagents with known antibody specificity to identify antigens present on red cells

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20
Q

Regeant red cells in transfusion

A

Red cells with known antigen specificity to identify antibodies present in plasma - eg might use group B regeant red cells to look for antiB antibodies present in patients plasma.

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21
Q

Agglutination of red cells

A

When red cells stick together in pre-transfusion testing to indicate a positive result for presence of antibodies in patients plasma corresponding to the regeant red cells (with the corresponding antigens present on the red cells) we have tested.

Eg.
Test patient’s red cells with anti-A, anti-B and anti-D antisera
– identify antigens on the red cells
– IgM reagents- direct agglutination

Test patient’s plasma against reagent red cells of group A and group B
2. – identify antibodies in the plasma
- Define the patient’s blood group

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22
Q

IAT crossmatch uses

A

• Agglutination indicates donor cells are incompatible with patient plasma
• Noagglutination- cells can be issued for transfusion

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23
Q

What does agglutination in pre-transfusion testing indicate?

A

Agglutination indicates the presence of an antibody and indicates donor cells are incompatible with patients plasma.

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24
Q

Indications for red cell transfusion

A

• Symptomatic anaemia Hb<70g/L (80g/L if cardiac disease)

• Major bleeding

• Always consider cause before transfusion
– Is there an alternative?

• Transfuse a single unit of red cells and then reassess patient

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25
Q

Indications for platelet transfusion

A

Prophylaxis in patients with bone marrow failure and very low platelet counts

• Treatment of bleeding in thrombocytopenic patient

• Prophylaxis prior to surgery/ procedure in thrombocytopenic patient

• Always consider the cause before transfusion

26
Q

Indications for FFP transfusion

A

Treatment of bleeding in patient with coagulopathy (PT ratio >1.5)

• Prophylaxis prior to surgery or procedure in patient with coagulopathy (PT ratio >1.5)

• Management of massive haemorrhage

• Transfuse early in trauma

• Not in absence of bleeding/ planned procedure

27
Q

Monitor patient during transfusion

A

Observations before blood is commenced

Observations at 15 minutes

Observations within 60 minutes of completion

28
Q

What are the major forms of haemoglobin?

A

HbA (2 alpha chains and 2 beta chains; α2β2 )

HbA2 (2 alpha and 2 delta; α2δ2)

HbF (2 alpha and 2 gamma; α2γ2)

29
Q

What are Haemoglobinopathies?

A

Hereditary conditions affecting globin chain synthesis
•Hundreds of mutations
•Behave as autosomal recessive disorders

30
Q

What are the two main group of haemoglobinopathies?

A

Thalassaemias; decreased rate of globin chain synthesis
–Structural haemoglobin variants; normal production of abnormal globin chain → variant haemoglobin eg HbS

31
Q

Thalassemias

A

Reduced globin chain synthesis resulting in impaired haemoglobin production
–Alpha thalassaemia; α chains affected
–Beta thalassaemia; β chains affected

32
Q

Consequences of thalassemias

A

Inadequate Hb production → microcytic hypochromic anaemia

•If severe: Unbalanced accumulation of globin chains which are toxic to the cell
•Ineffective erythropoiesis
•Haemolysis

33
Q

Alpha thalassemia

A

Mutations affecting α globin chain synthesis
•Results from deletion of one α+ (-α) or both α0 (–) alpha genes from chromosome 16
•Results in reduced α+ or absent α0 alpha chain synthesis from that chromosome
•α chains present in HbA, HbA2 and HbF therefore all are affected

34
Q

Classification of alpha thalassaemia

A

Unaffected = 4 normal α genes (αα/αα)

α thalassaemia trait; one or two alpha genes missing, asymptomatic carrier state, microcytic hypochromic red cells but ferritin normal

HbH disease; only one alpha gene left (–/-α ), moderate to severe anaemia

35
Q

Beta thalassaemia

A

• Disorder of beta chain synthesis
• Usually caused by point mutations
• Reduced ( β+), or absent ( β0 ) beta chain production depending on the mutation
•Only β chains and hence only HbA (α2β2) affected

36
Q

Classification of β thalassaemia

A

β thalassaemia trait (β+/β or β0/β)
•Asymptomatic, no/mild anaemia, low MCV/MCH, raised HbA2 diagnostic

β thalassaemia intermedia (β+/β+ or β0/β+)
•Moderate severity requiring occasional transfusion (similar phenotype to HbH disease)

β thalassaemia major (β0/β0)
•Severe, lifelong transfusion dependency

37
Q

Alpha Thalassaemia Trait

A

Asymptomatic carrier state, no Rx needed
•Microcytic, hypochromic red cells with mild anaemia
•Important to distinguish from iron deficiency ( but ferritin will be normal)

38
Q

HbH Disease

A

More severe form of alpha thalassaemia
•Only one working α gene per cell (–/-α )
•Anaemia with very low MCV and MCH

39
Q

Hb Barts Hydrops Foetalis Syndrome

A

Severest form of α thalassaemia - No α genes inherited from either parent (–/–)

Minimal or no α chain production →HbF and HbA can’t be made

No alpha chains to bind to so tetramers of Hb Barts (γ4) and HbH (β4) produced

40
Q

β Thalassaemia Major presenting features

A

Presents aged 6-24 months (as HbF falls) - Pallor, failure to thrive

Extramedullary haematopoiesis causing;
- Hepatosplenomegaly
- Skeletal changes
- Organ damage

Haemoglobin analysis: Mainly HbF, No HbA

41
Q

Management of β Thal Major

A

Regular transfusion programme to maintain Hb at 95-105g/l
•Suppresses ineffective erythropoiesis
•Inhibits over-absorption of iron
•Allows for normal growth and development
•Iron overload from transfusion then becomes the main cause of mortality

Bone marrow transplant may be an option if carried out before complications develop

42
Q

Consequences of Iron Overload

A

• Endocrine dysfunction
• Impaired growth and pubertal development
• Diabetes
• Osteoporosis
• Cardiac disease
• Cardiomyopathy
• Arrhythmias
• Liver disease
• Cirrhosis
• Hepatocellular cancer

43
Q

Management of Iron Overload

A

Iron chelating drugs (eg desferrioxamine) necessary

Chelators bind to iron which is then excreted

44
Q

Sickling Disorders pathophysiology

A

Point mutation in codon 6 of the β globin gene that substitutes glutamine to valine producing sickle cell shapes

This alters the structure of the resulting Hb→ HbS (α2βs2)

HbS polymerises if exposed to low oxygen levels for a prolonged period

This distorts the red cell, damaging the RBC membrane

45
Q

Sickle Cell Trait (HbAS)

A

One normal, one abnormal β gene (β/βs)
•Asymptomatic carrier state
•Few clinical features as HbS level too low to polymerise
•May sickle in severe hypoxia eg high altitude, under anaesthesia
•Blood film normal
•Mainly HbA, HbS <50%

46
Q

Sickle cell anemia

A

Sickle Cell Anaemia (HbSS)
• Two abnormal β genes (βs/βs)
• HbS > 80%, no HbA
• Episodes of tissue infarction due to vascular occlusion – sickle crisis
•Symptoms depend on site and severity
•Pain may be extremely severe
•‏ Chronic haemolysis – shortened RBC lifespan
• Sequestration of sickled RBCs in liver and spleen
• Hyposplenism due to repeated splenic infarcts

47
Q

Precipitants of Sickle Crisis

A

Hypoxia ‏
•Dehydration
•Infection
•Cold exposure
•Stress/fatigue

48
Q

Treatment of Sickle Crisis

A

•Opiate analgesia
•Hydration
•Rest
•Oxygen
•Antibiotics if evidence of infection
•Red cell exchange transfusion in severe crisis eg (lung) chest crisis or (brain)stroke

49
Q

Haemoglobinopathy Diagnosis

A

High performance liquid chromatography (HPLC) or electrophoresis to quantify haemoglobins present
•Identifies abnormal haemoglobins eg HbS
•Raised HbA2 diagnostic of beta thal trait

50
Q

Screening for Haemoglobinopathies

A

Antenatal screening to identify carrier parents now standard
•Family Origin Questionnaire and FBC
•Further testing if from high-risk area or abnormal RBC indices

51
Q

Management of Patients with alpha thalassaemia minima or trait

A

do not require treatment.

52
Q

Management of HbH disease

A

Transfusions: Haemoglobin typically ranges from 70-100 g/L. Transfusions may be needed for patients with Hb <70 g/L.

Iron overload: Patients undergoing regular transfusions are at risk of iron overload and secondary haemochromatosis. They usually require iron chelation therapy (e.g. Deferasirox).

Dietary supplementation: folic acid is usually recommended in patients with chronic haemolysis.

Splenectomy: may be considered to reduce transfusion requirements and hypersplenism (reduces number of circulating blood cells

53
Q

What are blood films?

A

A blood film involves a specialist examining the blood using a microscope to manually check for abnormal shapes, sizes and contents of the cells and note abnormal inclusions in the blood.

54
Q

Heinz Bodies

A

individual blobs seen inside red blood cells caused by denatured globin. They can be seen in G6PD and alpha-thalassaemia.

55
Q

Howell-Jolly bodies

A

individual blobs of DNA material seen inside red blood cells. Normally this DNA material is removed by the spleen during circulation of red blood cells. They can be seen in post-splenectomy and in patients with severe anaemia where the body is regenerating red blood cells quickly

Thus, they are seen in patients who have undergone splenectomy (as in this case) or who have functional asplenia (eg, from sickle cell disease). Target cells (arrows) are another consequence of splenectomy.

56
Q

Schistocytes

A

Schistocytes are fragments of red blood cells. They indicate the red blood cells are being physically damaged by trauma during their journey through the blood vessels. They may indicate networks of clots in small blood vessels caused by haemolytic uraemic syndrome, disseminated intravascular coagulation (DIC) or thrombotic thrombocytopenia purpura. They can also be present in replacement metallic heart valves and haemolytic anaemia

57
Q

Smudge cells

A

Smudge cells are ruptured white blood cells that occur during the process of preparing the blood film due to aged or fragile white blood cells. They can indicate chronic lymphocytic leukaemia.

58
Q

Spherocytes

A

are spherical red blood cells without the normal bi-concave disk space. They can indicated autoimmune haemolytic anaemia or hereditary spherocytosis.

59
Q

Normocytic Anaemia Causes

A

A – Acute blood loss
A – Anaemia of Chronic Disease
A – Aplastic Anaemia
H – Haemolytic Anaemia
H – Hypothyroidism

60
Q

Megaloblastic anaemia

A

Caused by B12 deficiency & Folate deficiency

61
Q

Normoblastic macrocytic anaemia is caused by:

A

Alcohol
Reticulocytosis (usually from haemolytic anaemia or blood loss)
Hypothyroidism
Liver disease
Drugs such as azathioprine

62
Q

IDA investigation findings

A

Low ferritin - highly specific for IDA, notmal ferritin can still be IDA too though

Both TIBC and transferrin levels increase in iron deficiency and decrease in iron overload

Transferrin sats low

Haemotology (9 decks)

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